How Does a Pressure Washer Work?

The pressure washer is a device or a machine used to clean the dirt at outdoors, rough surfaces, decks, stains on the floor, etc. There are some mechanical parts or components which gets combine to form a machine, which results in a fantastic cleaning.

If you are eager to know about the pressure washer and not aware of the main pressure washer parts and the working principle or how does a pressure washer work, then you are in the right place.

Here in this article, we will try to cover the parts or components of the pressure washer, which makes a pressure washer as a perfect cleaner as well as the working procedure of a pressure washer.

Firstly, let us discuss in brief about the main parts or components of the pressure washer, they are

  1. Electric Motor or Gasoline Engine
  2. Water Inlet
  3. Water Pump
  4. High-Pressure Hose
  5. Nozzle Attachments

1. Electric Motor or Gasoline Engine

pressure washer
pressure washer

The pressure washer is a combination of garden hose and air compressor. A pressure washer has either an electric motor or a fueled gasoline engine.

An electric motor pressure washer used in small work or light duty cleaning like in house cleaning where there is proper electrical supply.

Gasoline engines are beneficial for cleaning in large commercial spaces or heavy-duty cleaning where there is an inconvenience of electrical supply.

The engines are power rated around 3-4 kW like lawnmowers. The electric motor washer is densely packed and easy to carry around, but gas engines are more powerful and heavy-duty models. The primary function of this electric motor or gasoline engine is to power the water pump. 

2. Water Inlet

It acts as a connecting hose between the pressure washer and the central water supply. This water inlet has a filter inside, which prevents the entry of dust or debris inside the machine.

3. Water Pump

These water pumps are the heart of the pressure washer because of its role in pressure washer cleaning. These pumps can handle water flow at the rate of 1- 2 gallons per minute, i.e., 4 – 8 liters per minute.

It is a bit like a ground-water pump; only it is driven by an electric motor or gas engine at high speed. It has two steps of working; First, in one direction, when the driver pulls the pump, it begins to suck in water from the tap or supply. And in another step, water sprays out at high pressure.

4. High-Pressure Hose

Usually, an ordinary tube or hose wouldn’t have the capacity to withstand high-pressure water flow, so the tubing must be robust enough to split out the high-pressure water to clean the rough dirt wherever needed.

High-pressure hoses can withstand high pressure because of the material that made up of, so to provide enough ability, the tube is made up of high-density plastic along with wire mesh. You have to choose the hose such that its capacity, its rating must be higher than the pump in your pressure washer. For example, If your pressure washer rating is 2000 psi, then your hose must be able to withstand a minimum of 6000 psi.

5. Pressure Washer Nozzle Attachments

Pressure Washer Spray Nozzle Tips
Pressure Washer Spray Nozzle Tips

Nozzles are the tip part of the pressure washer where water comes out with high pressure. It takes control over the velocity, distance, and water flow direction. Nozzles have different angles for different types of cleaning, and it has color code for easy identification. 

a) Red Color (0 Degree)

As we know, red indicates danger, so be very careful with this red nozzle because it produces the most concentrated stream of water. You have to be very careful while handling this red nozzle, and if you are careless, then it damages the metal material, and even the user and others.

It is not only used for cleaning but also to remove weeds from between the cracks in concrete. It gets used to clean the specific spots. It is good to use in concrete areas to remove the stains and grime.

b) Yellow Color (15 Degree)

It is a medium jet spray angle which covers most area of the surface and results in a good cleaning job for removing tough dirt. It is not dangerous as zero degree or red nozzle, but have to be careful because it may damage soft metals and wood materials.

It is very supportive for cleaning the stripped paint, concrete floors, garage floors, and other heavy-duty cleaning jobs. Here water doesn’t spray out for a specific spot like zero degrees, and it gets spread over a wider angle to cover and clean most surfaces.

c) Green Color (25 Degree)

This nozzle is more than the yellow one, and it covers more surface than the yellow tip. It is a perfect nozzle for washing chores, patios, decks. This jet angle is solid enough to wash the leaves away from the areas.

If you can handle with care, then it can be used to wash away the dirt from cars, boats, trucks using chemicals or detergents. It is also best for general cleaning.

d) White Color (40 Degree)

It is a safe nozzle that covers and clean most surfaces at low pressure. Its spectrum is comparatively opposite to zero degrees angle. If you are not comfortable or satisfied with the green nozzle to wash cars or boats, then you can choose the white tip.

It is suitable for using to wash windows, and it cleans the large surfaces quickly.

e) Black Color (65 Degree)

It is the most important, more full angle tip in this attachment, and it is the safest tip for cleaning purposes. Sometimes it is also known as the detergent nozzle because of its low velocity and wider pressure angle. It cleans the soaping, like pre-washing – before using the pressure washing.

After using this soaping nozzle for prewash, then you have to switch to other tips for pressure washing.

f) Rotary Nozzle

It gets considered to be the accessory of the pressure washer. It is almost an alternative to the red tip. The output of this nozzle, i.e., the water that comes out from this nozzle rotates in a circular motion in the range between 5,000 to 9,000 rpm of jet stream cleaning power.  

It can expand about 15-degree wand patterns, and it has 4-8 inch spray circle cleaning with high pressure to produce good wash results. The result will be 50 percent more than expected cleaning, and it takes half of the regular cleaning period. It is used on concrete to remove thick grime, dirt, strip paint, rust, and also the gum that detach on sidewalks.

g) Detergent Nozzle

This detergent nozzle also considered as an accessory used in the area above the ground, which applies the detergent up to 30 feet. 

Until now we get to know about the main components of the pressure washer. Now let us see how do all these mechanical components work together to give results of cleaning.

How Does Pressure Washer Work?

Generally, water cannot be compressed; If we apply pressure to a container filled with water, then water distributed equally in every direction as well as for every single molecule in the box towards outside. Every pressure washer works on the principle of ‘Pascal Law.’

This Pascal law states – “ When pressure is applied at any point in a fluid that has been stored in a container, it is distributed in all directions in an equal manner and also to all points of the fluid.” This is the law used everywhere when it comes to fluid dynamics.

As said above, pressure washer works with similar principles of fluid dynamics, i.e., ‘Pascal Law.’ Its working procedure is dependent on three main contents namely,

  • Power Source
  • Pump
  • High-Pressure Nozzle

A toggle switch is present in the machine to take control over the water like a release or holding within the tank.

Pressure Washer Cleaning

Power Source

The power source of a pressure washer may be an electric motor or gas engine. Whether its an electric motor or gasoline engine, the working principle remains the same.

When starter rope pulled, the starter engages the flywheel that is attached, which leads to rotation of the crankshaft (a shaft driven by a crank). The crankshaft has a connection with a piston, which has a linear movement of up and down.

The linear momentum of piston and rotation of the crankshaft together give way for the beginning of ignition (the process that starts to burn) process. Flywheel has a permanent magnet in it, and as it rotates, it creates a magnetic field.

Most pressure washers use a four-cycle engine to drive the pump. The four cycles or stroke function which results in complete working is as follows,

Intake Stroke – As the piston moves down, the inlet valve opens, and a mixture of fuel and air enter into the cylinder through carburetter.

Compression Stroke – As a mixture enters, the inlet valve closes, and the piston moves up and leads to compression before ignition of the combination of fuel and air.

Power Stroke – After compression of the mixture, ignition takes place as a spark plug create the fire and ignites the compressed mixture, which forces the piston to move down.

Exhaust Stroke – The force of the spinning of the flywheel makes the piston again to move up, as it moves up the exhaust valve opens, and combustion gas exits through the engine muffler or silencer.

The engine repeats and runs on this four-cycle until they turned off.


Generally, the pump run by two main components, i.e., piston and cylinder. It gets driven by a pull cord which draws momentum from the engine. It’s working is the same as a syringe. Crankcase (a cover which encloses the crankshaft) in the machine consists crankshaft (a shaft driven by a crank) which has a connection to a set of the plunger (a part of device works with plunging movement, i.e., jumping movement which is three in number) in the pump. Plunger’s function is to suck or eject the water, whose purpose is similar to a piston in the engine.

  Pressure Washer Pump

The plunger works in connection with a cam. As said above, its function is to suck water, so each plunger sucks water from a temporary reservoir that stores water from the source. Plunger holds up the water until the water gets used up as well as it allows space for new water to get in.

Plunger working movement is in the form of up and down. When it moves up, through an input check valve, water gets drawn into a containing cylinder. When the plunger moves down, through an output check valve, water gets forced to step outside into an unloader.   

High-Pressure Nozzle

The high-pressure nozzle has a trigger a gun which is very long and narrow. The unloader connected to a trigger switch, which gets compressed to release the high pressurized water out through a nozzle, which results in top cleaning with high-pressure water. When it was released or untriggered, water flow stops.

When water flow stops or a gun is untriggered, a spring valve present in the machine detects stopped water flow and allows the water to move back to the reservoir. As well as this valve mechanism allows the motor to run even when stream terminates to flow.

This process continues until the trigger compressed or triggered again. During this working process, if the temperature of the water exceeds its limit, there is a release valve in the machine which flush the hot water out and bring space for cold water to flow inside. 

Some pumps have a chemical pipe injection port at the output pipe to introduce the detergent into the water. To get an efficient result, you have to choose a low-pressure nozzle to draw soap or detergent to the hose and outlet pipe. This whole working process completes in seconds together, which we never get to know because of its fast working.

Common Ratings of a Pressure Washer

You can buy a pressure-based two terms, i.e., PSI (Pounds per Square Inch) and GPM (Gallons Per Minute). The Overall performance of the pressure washer can be decided based on these two things, so the higher the number or rating performance is also higher.

PSI – Pressure of water is measured in pounds per square inch and at the output. It powers you to sneak into the rough dirt.

GPM – The flow rate of the water delivered to the trigger gun is measured in terms of gallons per minute. It provides the power to wash away the dirt.

Maintenance Tips

  • Improper functioning of the pressure washer will take place if you are not using the right fuel for the engine.
  • Every time before starting the machine, make sure that you have flushed out the air from the inlet pipe; otherwise, it leads to damage to the valves in the engine.
  • If there is an insufficient water supply, you have to face problems with the pressure washer.
  • Oil the pump regularly and periodically, which prevents and protects the piston and other moving components from overheating, and sometimes even pump failure.
  • Carburetter must be clean; when there is a need to replace, you have to replace it.
  • Use detergents like pump saver, which is a mild one; because using strong detergent may lead to damage piston and seals.


1. Do power washers use a lot of water?

Ans. An average pressure washer uses 8 GPM(gallons per minute) or 30.2 liters/min when there is low pressure. If pressure increases, pressure washer use 5 GPM, i.e., 18.9 liters/min is sufficient.

2. Is it safe to use a pressure washer on a car?

Ans. You can use a pressure washer, which has a rating around 1200 – 1900 PSI. This rating is sufficient to wash your vehicle without worries. It won’t damage any paint or parts of your car.

3. Do you turn the water on before starting a pressure washer?

Ans. Yes, because of turning on before starting the pressure washer, air bubbles in the hose get to flush out from the pipe.

4. How fast does water come out of a pressure washer?

Ans. The flow rate of the pressure washer depends on the scale of GPM. If you need the fastest rate, then you have to choose 0-degree nozzle whose speed is around 243 mph, else you can select other degree nozzles if you some less speed.


Finally, we come across the discussion on the main components and how does the pressure work of the pressure washer. Buy the best pressure washer, depending on your needs. You have to follow the maintenance tips to keep your cleaning machine in good working condition.


Pressure Washer Nozzle Colors Explained In Plain English

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Hi, I'm James. The Chief Editor at I worked in Pressure Washer industry for a few years, and I thought to share my knowledge about pressure washer on our blog with my team.

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